The present disclosure relates to hopper cars, and more particularly, hopper cars having a through center sill.
To accommodate the widely varying types of cargo that may travel over a railroad, rail cars of many different designs are manufactured, and in some instances a rail car will be specially designed to carry either one specific type of cargo (e.g. automobiles carried in a freight car with multi-level decks), or cargo having a certain characteristic (e.g. perishable cargo in an insulated and/or refrigerated car). One type of cargo that is often transported via railroad is cargo having bulk fluid properties, meaning commodities that, in bulk, exhibit fluid-like behavior. Examples of such commodities are grain, nuts, etc. Although such cargo could conceivably be packaged in bags and transported by boxcar, for example, such a method would be highly inefficient. Instead, such bulk fluid cargo is typically transported in a hopper car, which is specially designed to carry cargo having bulk fluid properties.
A hopper car usually includes one or more cargo-carrying bins, called cargo wells, which may be filled with grain or other bulk fluid cargo. The cargo-carrying capacity of a typical existing hopper car is usually within the approximate range of 3200 to 6200 cubic feet and/or the range of 220,000 to 232,000 lbs. The cargo is typically poured into the hopper car from the top and discharged from the bottom. To facilitate loading a hopper car with bulk fluid cargo, the hopper car will typically include a large opening over the top of each cargo well. Although some hopper cars include covers to protect the cargo from the elements during transport, such covered hopper cars will include a large lid that may be opened to load cargo, and an uncovered hopper car may even have cargo wells that are completely open at the top.
Cargo in a hopper car is usually discharged through respective discharge outlets at the bottom of each cargo well. Each discharge outlet is selectively closeable to permit the loading and transporting of the cargo. The discharge outlets are usually located approximately at the center of the cargo well that they respectively empty. When the discharge outlet is opened, the bulk fluid cargo empties from the hopper car. To facilitate the fluid flow of cargo towards these outlets while a hopper car is being emptied, each cargo well will usually include at least one pair of opposed side walls, or slope sheets, that are each respectively slanted downwardly and inwardly towards the respective outlet at the center of the cargo well.
One specific type of hopper car is a through center sill hopper car. A hopper car, like other rail cars, is structurally supported by an undercarriage that includes a center sill oriented longitudinally along the approximate center line of the hopper car. A through center sill hopper car has a center sill that runs through the respective cargo wells of the hopper car, such that when loaded, the cargo in each cargo well will surround the center sill. In order to facilitate the flow of cargo around the center sill when the cargo is unloaded, the center sill is typically covered by a triangular hood so that the bulk fluid cargo does not collect on top of the center sill when the hopper car empties. Positioning a center sill inside the cargo wells of a hopper car reduces somewhat the cargo-carrying capacity of the hopper car.
The center sill is a primary load-bearing structural member of the hopper car, and must be of a sufficiently sturdy construction to withstand not only the substantial standing weight of both the hopper car and the cargo it carries, but also the various bending and rotational stresses that are applied to the center sill as the hopper car moves along a railroad track. The center sill is typically constructed of two sets of opposed, parallel pieces of elongate steel or other similarly rigid material, forming a square cross-section. These individual members are usually welded together along the right-angle intersections between adjacent members, and are typically fashioned of steel or other similarly rigid material 1/2 -inch thick or greater so as to withstand the aforementioned loads and stresses. Often, the center sill is further reinforced by a plurality of gussets or other reinforcements inside the center sill. Like the center sill, other load-bearing structural members of the hopper car, such as the slope sheets, the side sills, end sills, etc. must also have sufficient strength to withstand such weight and stresses, and are likewise fashioned of steel or other material with thicknesses sufficient to withstand the loads and stresses incident to the carrying capacity of the hopper car.
Unfortunately, though required by the design of existing hopper cars, the aforementioned size and composition of the structural members, such as the center sill, substantially add to the weight of the hopper car. What is desired, therefore, is a new design for a hopper car that is lighter in weight than existing hopper cars, yet is able to durably withstand the same loads and stresses as do existing hopper cars of similar carrying capacity.